Selection of the promising almond (Prunus amygdalus L.) genotypes among seedling origin trees

Scientia Horticulturae 256 (2019) 108587

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Selection of the promising almond (Prunus amygdalus L.) genotypes among seedling origin trees

T

Ali Khadivi , Leila Safdari, Mohammad-Hossein Hajian, Fateme Safari ⁎

Department of Horticultural Sciences, Faculty of Agriculture and Natural Resources, Arak University, 38156-8-8349, Arak, Iran

ARTICLE INFO

ABSTRACT

Keywords: Almond Breeding Yield Kernel quality Genetic resource

Almonds, Prunus amygdalus L., are among the most popular tree nuts on a worldwide basis and rank first in tree nut production. The present study was carried out on 187 almond seedling origin trees to select the superior genotypes based on morphological and pomological characters. Significant differences were found among the studied genotypes. Nut weight ranged between 1.20 and 6.68 g with an average of 3.50, while kernel weight ranged from 0.39 to 2.06 g with an average of 0.93. The average of double kernels and blank nuts was 15.11% and 4.04%, respectively. Kernel weight showed positive correlations with leaf and nut dimensions. Principal component analysis (PCA) indicated 16 components that explained 72.51% of the total variance and nut and kernel dimensions and weight made the biggest contribution in distinguishing the genotypes. Regarding ideal values of the important and commercial characters of almond such as fruit yield, nut weight, shell hardness, kernel shape, kernel weight, and kernel taste, 24 genotypes were superior and could be used as a parent in breeding programs and also might be singled out directly for cultivation in the orchards.

1. Introduction The almond tree [Prunus dulcis (Mill.) DA Webb; syn. P. amygdalus (L.) Batsch] is a species of the Rosaceae family commercially cultivated worldwide for its kernels. For several centuries, the almond has been propagated mainly by seed. The extensive exchange of almond in the fourth century BC led to the differentiation of two groups: Mediterranean species and Central Asia species (Socias i Company, 1998). The almond tree has evolved very slowly by seedlings until the nineteenth century (Grasselly and Crossa-Raynaud, 1980). Almond cropping in several countries is often associated with the selected seedling populations. The types adapted to specific production areas have emerged through natural selection and human selection pressure (Grasselly and Crossa-Raynaud, 1980). Over time, a transition occurred from an agroforestry system characterized by a large phenotypic diversity to a semi-intensive and intensive commercial system that relies particularly on the use of locally selected varieties. Almond has relatively good benefits because of the suitable ecological conditions and its resistance to the drought and the calcareous conditions (Grasselly and Crossa-Raynaud, 1980). Outbreeding events are enhanced by the species gametophytic selfincompatibility (Socias i Company, 1998) and therefore contribute to the extension of genetic diversity. In addition, most of the almond trees

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grown in Iran are mainly raised from seeds and exhibit tremendous variability in tree, foliage, floral and fruit characters. In addition, the climatic diversity and high heterozygosity because of continuing sexual propagation have formed a very rich genetic material among local almond populations in Iran. More variability within a species can give better chances for elite selection. Information on the nature and degree of genetic diversity present in seedling trees of almond can help in the selection of trees for further species improvement (Khadivi-Khub and Etemadi-Khah, 2015). The assessment of genetic diversity and relationships between almond varieties is of great importance in the determination of gene pools, development of conservation strategies and identification of genetic resources (Gradziel et al., 2001). Morphological studies are still used as the basis and the first step in the evaluation of germplasm (Khadivi-Khub and Anjam, 2014). The collection, evaluation and also identification of superior genotypes from native populations are one of the main methods in almond breeding programs. Selection of the superior almond genotypes is based on climatic adaptation, high production and high quality of kernel and nut. In this method, in addition to variation, an environmentally-friendly genotype is also created (Talhouk et al., 2000). In Iran, due to the lack of recognition of favorable genes and plant genetic resources, breeding programs have not paid much attention to

Corresponding author. E-mail address: [email protected] (A. Khadivi).

https://doi.org/10.1016/j.scienta.2019.108587 Received 14 May 2019; Received in revised form 14 June 2019; Accepted 14 June 2019 0304-4238/ © 2019 Elsevier B.V. All rights reserved.

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A. Khadivi, et al.

fruit crops. The first and most important action is the selection of native genotypes with superior characteristics. Almond genotypes with lateblooming can be cultivated in the areas where the late frosts are frequent. Genetic variation of native almond populations presents many opportunities for breeding and introducing the promising trees. The aim of the present research was to identify the superior almond genotypes that will be further exploited through breeding programs for their tree, flowering time and nut characteristics or for direct cultivation.

(13.17%), kernel length (13.75%), suture opening of the shell (15.44%), and kernel thickness (16.85%) showed the lowest variation and their CV was lower than 20.00% (Table 1). Similarly, it has been reported that kernel length, kernel width, and kernel thickness showed the lowest CVs, while double kernel showed the highest ones (De Giorgio et al., 2007; Fathi et al., 2008; Gouta et al., 2019). The variables with low CVs are more homogeneous and repeatable among genotypes, while the characters with high CV values are more discriminating and can be reliable markers for the characterization of genotypes. Tree growth habit was drooping (50 genotypes), spreading (50), spreading to upright (56), upright (23), and extremely upright (8) (Table 2). In the study of Tunisian almonds, Gouta et al. (2019) reported that the majority of the described trees (85%) had an upright, spreading or drooping form, while a minority (15%) showed an extremely upright or weeping habit. The extremely upright habit observed in the present study can be used to meet less immediate breeding needs (Gradziel et al., 2002). In fact, extremely upright and upright genotypes are the main characteristics required for high and super highdensity systems, and the current tendency towards intensification in many species such as olive may affect almond in the near future, especially given that the first results have been so promising (Miarnau et al., 2013; Rius et al., 2013). The studied genotypes showed large differences in tree growth vigor, so that vigor of genotypes was generally found to be weak (42), intermediate (88), and strong (57). Gouta et al. (2019) observed that the majority of almond trees (70%) from a collection in Tunisia showed intermediate growth vigor. The dominant tree height was high (87 genotypes). Canopy density, branching, branch density, and branch flexibility varied from low to high and intermediate situation was predominant for those characters (Table 2). Leaf density ranged from low to high. Four types of leaf shape were distinguished including flat (51 genotypes), ovate (59), narrow-elliptic (9), and elliptic (68). Leaf serration shape was predominantly serrulate (133). Leaf apex shape was predominantly acute (139 genotypes) (Table 2). Branch leaf length ranged from 29.29 to 96.81 mm, while branch leaf width varied from 11.14 to 53.74 mm. The range of 5.82–33.71 mm was recorded for branch petiole length. Spur leaf length ranged from 23.14 to 70.30 mm, while spur leaf width varied between 8.16 and 39.81 mm. The range of 5.06–36.82 mm was recorded for spur petiole length (Table 1). The small leaves likely indicate adaptation to the xerophytic conditions (rainfall less than 150 mm per year). Similarly, Lansari et al. (1994) found that phenotypes collected from local almond populations in Morocco tended to have smaller leaves than introduced cultivars. This tendency was also observed in wild almond species in dry conditions in Iran (Sorkheh et al., 2009; Khadivi-Khub and Anjam, 2014, 2016; Khadivi-Khub et al., 2016). The development of drought-resistant almond production systems using native germplasm would, therefore, make more sustainable production possible, particularly in marginal areas with harsh climate conditions (Gouta et al., 2019). The flower buds were mainly formed on spurs in the majority of genotypes (120 genotypes), whereas distribution was mixed in 50 genotypes, in agreement with the previous findings (Colic et al., 2012; Zeinalabedini et al., 2012; Khadivi-Khub and Etemadi-Khah, 2015; Khadivi-Khub and Osati, 2015). There were large variations in ripening date (11 August to 12 September) between the studied genotypes. A one-month later harvesting season for these genotypes is an important element and makes them as the promising genotypes for future almond breeding. Fruit yield varied from very low to very high and most of the genotypes (57) showed high yield. The genotypes were clustered into five groups based on nut shape including round (24 genotypes), ovate (79), oblong (33), cordate (45), and extremely narrow (6). Nut length ranged from 20.53 to 42.70 mm, while nut width varied from 13.63 to 26.49 mm. Nut weight ranged between 1.20 and 6.68 g with an average of 3.50. Colic et al. (2012) reported the range of 2.53–6.00 g for nut weight in almond. Zeinalabedini et al. (2012) recorded

2. Materials and methods 2.1. Plant material The present study was carried out on 187 almond seedling origin trees from Arak region, Markazi province, Iran. Arak region is located in the center of Iran (34°05′30″N, 49°45′10″E, 1708 m above sea level) with 13.80 °C mean annual temperature and 320 mm annual rainfall. The selected mature seedling origin trees were named and labeled based on their region area. The selected trees were healthy and had a full crop. Fertilization, irrigation and, other cultural practices were regularly carried out. 2.2. Morphological and pomological evaluations Morphological and pomological characterization of the genotypes was performed according to the guidelines provided by the International Plant Genetic Resources Institute (IPGRI) (Gulcan, 1985). In total, 47 phenotypic and pomological characteristics, comprising 18 quantitative and 29 qualitative traits, were used to assess the range of morphological variation among the genotypes (Table 1). Measurements of nut and kernel traits were based on 50 replicates and the mean values were used. Variables such as leaf dimensions (length and width) and fruit size (length, width, and thickness) were measured by a digital caliper. Nut and kernel weight was measured by an electronic balance with 0.01 g precision. The traits including tree growth habit, tree growth vigor, tree height, trunk color intensity, trunk diameter, canopy density, branching, branch density, branch flexibility, leaf density, leaf shape, leaf serration shape, leaf upper surface color, leaf lower surface color, leaf apex shape, location of flower bud, fruit yield, nut apex shape, nut shape, shell hardness, shell color intensity, shell retention, suture opening of the shell, marking of outer shell, kernel shape, kernel color intensity, kernel shriveling, kernel pubescence, and kernel taste were qualitatively estimated based on rating and coding described into the almond descriptor (IPGRI) (Gulcan, 1985). 2.3. Statistical analysis Significant differences were determined between the measured traits using analysis of variance (ANOVA) by SAS software (SAS Institute, Cary, NC, USA, 1990). The coefficients of variation (CV) were calculated as the variance index. Correlation between the traits was determined using Pearson correlation coefficient by SPSS® software version 16 (SPSS Inc., Chicago, IL, USA, Norusis, 1998). The relationships between the genotypes were assessed using principal component analysis (PCA) using SPSS® software. In addition, bi-plot and tri-plot were generated using SPSS statistics software. 3. Results and discussion 3.1. Genotype characterization The ANOVA (P ≤ 0.01) revealed significant differences among the studied genotypes based on the characters measured (data not shown). The highest CV was found for blank nut percentage (256.83%) and followed by double kernel percentage (134.43%), whereas nut diameter (10.46%), kernel width (12.01%), nut width (12.51%), nut length 2

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Table 1 Descriptive statistics for the morphological traits utilized in the studied almond genotypes. No.

Character

Abbreviation

Unit

Min.

Max.

Mean

SD

CV (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Tree growth habit Tree growth vigor Tree height Trunk color intensity Trunk diameter Canopy density Branching Branch density Branch flexibility Branch leaf length Branch leaf width Branch petiole length Spur leaf length Spur leaf width Spur petiole length Leaf density Leaf shape Leaf serration shape Leaf upper surface color Leaf lower surface color Leaf apex shape Location of flower bud Fruit yield Harvest date Nut apex shape Nut shape Nut length Nut width Nut diameter Nut weight Shell hardness Shell color intensity Shell retention Shell thickness Suture opening of the shell Marking of outer shell Kernel length Kernel width Kernel thickness Kernel weight Kernel shape Kernel color intensity Kernel shriveling Kernel pubescence Kernel taste Double kernel percentage Blank nut percentage

TrGrHa TrGrVi TrHe TrCoIn TrDi CaDe Br BrDe BrFl BrLLe BrLWi BrPeLe SpLLe SpLWi SpPeLe LDe LSh LSeSh LUpSuCo LLoSuCo LApSh LoFlBu FrY HaDa NuApSh NuSh NuLe NuWi NuDi NuWe SheHa SheCoIn SheRe SheTh SuOpShe MaOuShe KeLe KeWi KeTh KeWe KeSh KeCoIn KeShr KePu KeTa DoKePer BlNuPer

Code Code Code Code Code Code Code Code Code mm mm mm mm mm mm Code Code Code Code Code Code Code Code Date Code Code mm mm mm g Code Code Code mm Code Code mm mm mm g Code Code Code Code Code % %

1 1 1 1 1 1 1 1 1 29.29 11.14 5.82 23.14 8.16 5.06 1 1 1 1 1 1 1 1 11-Aug 1 1 20.53 13.63 10.23 1.20 1 1 1 1.09 1 1 12.74 7.97 4.67 0.39 1 1 1 1 1 0.00 0.00

9 5 5 7 5 5 5 5 5 96.81 53.74 33.71 70.30 39.81 36.82 5 7 3 5 5 3 5 9 12-Sep 3 9 42.70 26.49 19.79 6.68 9 7 5 4.46 5 5 29.96 18.52 14.63 2.06 9 9 5 5 5 90.00 90.00

3.81 3.16 3.58 5.35 2.76 2.76 2.90 2.91 2.93 59.20 20.30 18.98 43.38 15.62 15.75 3.09 4.01 1.58 2.66 2.18 2.49 4.10 4.72 26-Aug 1.73 4.25 30.73 19.92 15.77 3.50 4.82 3.94 4.72 2.89 4.74 2.54 21.99 12.21 6.93 0.93 4.76 5.29 2.33 1.65 4.13 15.11 4.04

2.27 1.45 1.50 2.37 1.72 1.51 1.54 1.52 1.52 13.44 5.40 4.59 9.67 4.90 4.85 1.66 2.48 0.91 1.28 1.22 0.88 1.31 2.42 2.63 0.97 2.16 4.05 2.49 1.65 1.12 2.11 1.65 0.98 0.62 0.73 1.56 3.02 1.47 1.17 0.27 1.78 1.79 1.49 0.96 1.23 20.31 10.38

59.53 45.89 41.84 44.30 62.28 54.57 53.17 52.30 51.71 22.70 26.58 24.21 22.30 31.39 30.77 53.62 61.72 57.53 48.23 56.01 35.18 32.05 51.27 55.41 55.78 50.92 13.17 12.51 10.46 31.95 43.82 41.88 20.70 21.30 15.44 61.42 13.75 12.01 16.85 29.42 37.39 33.86 64.12 58.36 29.69 134.43 256.83

22.00–42.00 mm for nut length, 16.00–30.00 mm for nut width, and 1.00–7.00 g for nut weight. Shell thickness varied from 1.09 to 4.46 mm. Light shell color intensity, low marking of the outer shell, and very wide suture opening of the shell were dominant. The genotypes were clustered into five groups based on shell hardness including extremely hard (18 genotypes), hard (47), semi-hard (68), soft (42), and paper (12). Shell softness is connected to important breeding issues. Hard-shell genotypes are reported to be more resistant to insect and fungal infestation, while soft-shell genotypes are highly susceptible to insect and fungal damage (Ledbetter and Shannard, 1992; Gradziel and Martinez-Gomez, 2002; Khadivi-Khub and Etemadi-Khah, 2015). The breeding strategy thus depends on the genotype used: in the case of soft shell genotypes, it is necessary to search for a source of insect and fungal resistance, whereas in the case of semi-hard shell genotypes, it is necessary to choose from the existing germplasm to preserve acceptable shelling rates. The genotypes were clustered into five groups based on kernel shape including extremely flat (12), flat (47), intermediate (82), oblong (43), and extremely oblong (3). Kernel taste was sweet in the majority of genotypes (118). Kernel length ranged from 12.74 to 29.96 mm and kernel width varied from 7.97 to 18.52 mm, while kernel thickness was

between 4.67 and 14.63 mm (Table 1). Zeinalabedini et al. (2012) recorded the range of 10.00–30.00 mm for kernel length and 10.00–17.00 mm for kernel width. Kernel weight ranged from 0.39 to 2.06 g with an average of 0.93. Kernel weight average with approximately 1.00 g is common in many European and American cultivars, and such weight is a desired trait in breeding programs (Gradziel and Kester, 1998). In the present study, the value of kernel weight in 66 out of 187 studied genotypes was higher than 1.00 g. Colic et al. (2012) recorded the range of 0.62–1.29 g for this trait. In addition, Zeinalabedini et al. (2012) recorded the range of 0.50–2.30 g for kernel weight. Kernel color that is an important characteristic from a commercial viewpoint varied from extremely light to extremely dark, although it was predominantly intermediate in most of the genotypes (73). Slightly wrinkled kernel shriveling was dominant and agreed with previous results (Zeinalabedini et al., 2012; Colic et al., 2012; Khadivi-Khub and Etemadi-Khah, 2015). Kernel pubescence ranged from low to high, although it was predominantly low in most of the genotypes (94). Double kernel percentage ranged from 0.00 to 90.00% with an average of 15.11%. In general, 90 out of 187 studied genotypes did not show this phenomenon and only 19 genotypes showed more than 50% 3

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Table 2 Frequency distribution for the measured qualitative morphological characters in the studied almond genotypes. Character

Code and frequency (no.) 1

3

5

7

9

Tree growth habit Tree growth vigor Tree height Trunk color intensity Trunk diameter Canopy density Branching Branch density Branch flexibility Leaf density Leaf shape Leaf serration shape Leaf upper surface color Leaf lower surface color Leaf apex shape Location of flower bud Fruit yield Nut apex shape Nut shape Shell hardness Shell color intensity Shell retention Suture opening of the shell Marking of outer shell Kernel shape Kernel color intensity Kernel shriveling Kernel pubescence Kernel taste

Drooping (50) Weak (42) Low (33) Gray (29) Low (81) Low (65) Low (60) Low (58) Low (57) Low (60) Flat (51) Serrulate (133) Light green (57) Light green (89) Oblate (48) One year old shoot (17) Very low (29) Oblate (119) Round (24) Extremely hard (18) Extremely light (19) None retained (11) Excellent seal/no opening (2) Low (83) Extremely flat (12) Extremely light (5) Low (94) Low (127) Bitter (12)

Spreading (50) Intermediate (88) Intermediate (67) Cupric (30) Intermediate (47) Intermediate (79) Intermediate (76) Intermediate (79) Intermediate (80) Intermediate (59) Ovate (59) Serrate (34) Green (105) Green (86) Acute (139) Mixed (50) Low (51) Acute (68) Ovate (79) Hard (47) Light (82) Partly missing (4) Open/about 2 mm (20) Intermediate (64) Flat (47) Light (40) Intermediate (62) Intermediate (59) Intermediate (57)

Spreading to upright (56) Strong (57) High (87) Red (7) High (59) High (43) High (51) High (50) High (50) High (68) Narrow-elliptic (9) – Dark green (25) Dark green (12) – Spur (120) Intermediate (37) – Oblong (33) Semi-hard (68) Intermediate (65) All retained (172) Very wide (165) High (40) Intermediate (82) Intermediate (73) High (31) High (1) Sweet (118)

Upright (23) – – Dark (121) – – – – – – Elliptic (68) – – – – – High (57) – Cordate (45) Soft (42) Dark (21) – – – Oblong (43) Dark (61) – – –

Extremely upright (8) – – – – – – – – – – – – – – – Very high (13) – Extremely narrow (6) Paper (12) – – – – Extremely oblong (3) Extremely dark (8) – – –

Table 3 The values of the most important fruit traits for the selected superior almond genotypes in the present investigation. Genotype

Fruit yield

Nut shape

Nut length (mm)

Nut width (mm)

Nut weight (g)

Shell hardness

Kernel length (mm)

Kernel width (mm)

Kernel weight (g)

Kernel shape

Kernel taste

Double kernels (%)

Blank nuts (%)

Khalaj-4 Ghanat-14 Ghanat-12 Karchan-2 Ghanat-15 Ghanat-1 Zolfaghar-1 Ghanat-10 Evand-44 Anaj-6 Karchan-1 Ghanat-4 Ghanat-6 Molabagher-1 Javersian-5 Ghanat-16 Zolfaghar-3 Zolfaghar-2 Javersian-12 Molabagher-16 Karchan-7 Nodeh-7 Karchan-5 Ghanat-11

High Intermediate High High Intermediate High Intermediate Intermediate High Very high Intermediate Intermediate Intermediate Intermediate High Intermediate High High High Intermediate Intermediate High High Intermediate

Ovate Oblong Cordate Cordate Ovate Oblong Cordate Oblong Round Ovate Oblong Oblong Cordate Cordate Ovate Oblong Oblong Oblong Cordate Cordate Ovate Ovate Ovate Oblong

37.92 37.54 35.60 40.43 33.21 33.83 38.53 31.56 29.80 27.11 32.70 32.58 34.96 35.61 31.70 32.16 31.67 33.59 37.87 38.03 33.79 29.28 34.46 35.43

23.25 24.96 21.89 22.00 21.47 22.70 24.72 21.20 21.86 24.37 23.45 23.88 20.98 22.31 20.19 20.25 22.37 23.66 23.69 24.27 20.50 22.73 21.70 22.55

6.05 5.05 4.46 5.07 4.15 5.16 6.23 5.31 4.78 5.41 5.37 4.50 4.62 4.01 3.17 3.65 3.83 4.78 5.72 4.57 3.76 4.62 4.46 4.23

Hard Soft Hard Semi-hard Soft Hard Soft Hard Hard Hard Hard Hard Hard Paper Semi-hard Semi-hard Hard Semi-hard Semi-hard Paper Semi-hard Hard Hard Hard

29.26 27.52 27.34 29.96 24.68 25.59 28.50 24.63 20.99 17.46 25.02 23.17 27.53 27.35 21.07 23.94 22.89 24.72 27.25 28.40 24.80 22.57 25.34 24.63

15.60 15.10 14.48 15.34 14.76 14.99 14.20 14.20 13.15 14.34 15.17 14.45 13.93 14.40 11.90 14.37 13.31 13.79 14.21 13.41 13.04 12.57 13.85 14.56

2.06 1.77 1.75 1.72 1.65 1.61 1.49 1.46 1.46 1.44 1.41 1.38 1.38 1.32 1.30 1.29 1.27 1.27 1.26 1.25 1.23 1.21 1.21 1.20

Oblong Flat Oblong Oblong Flat Flat Flat Flat Oblong Oblong Flat Flat Flat Flat Oblong Flat Flat Flat Flat Oblong Oblong Oblong Oblong Flat

Sweet Sweet Sweet Intermediate Sweet Sweet Intermediate Sweet Sweet Intermediate Intermediate Intermediate Intermediate Sweet Sweet Intermediate Intermediate Intermediate Sweet Intermediate Sweet Sweet Intermediate Sweet

10.00 0.00 20.00 0.00 10.00 10.00 10.00 10.00 10.00 20.00 0.00 20.00 0.00 0.00 10.00 30.00 20.00 0.00 0.00 20.00 25.00 20.00 0.00 10.00

0.00 0.00 0.00 0.00 0.00 0.00 20.00 10.00 0.00 0.00 0.00 0.00 0.00 10.00 5.00 0.00 0.00 0.00 0.00 10.00 10.00 0.00 0.00 0.00

doubled kernels. This phenomenon is due to the fertilization of two ovules in the almond ovary and then the development of both ovules. This is considered to be a negative trait because it results in two deformed kernels of low commercial value. In addition, it decreases fruit quality depending on the double kernel proportion (Kester and Gradziel, 1996). Nevertheless, the influence of the environment on the expression of this trait (especially low temperatures during the preblooming stage) has been well documented (Egea and Burgos, 1995;

Artega and Socias I Company, 2001). The application of an equilibrated fertilizer program and the cultivation of the susceptible ecotypes in more clement zones may reduce this problem (Gouta et al., 2019). Blank nut percentage varied from 0.00 to 90.00% with an average of 4.04%. In general, 142 out of 187 studied genotypes did not show this disorder and formed kernel, while only three genotypes had more than 50% blank nuts. Sorkheh et al. (2010) suggested that this trait is associated with the fertility degree. Thus, it seems that the majority of the 4

TrGrHa

1 0.03 −0.04 −0.27** −0.24** −0.10 −0.20** −0.17* 0.21** −0.07 −0.08 −0.09 −0.02 0.03 −0.07 −0.04 −0.10 −0.20** 0.06 0.06 0.05 −0.14 0.19** −0.07 −0.03 0.02 0.00 0.01 0.06 0.01 −0.15* 0.07 0.02 0.02 0.06 −0.01 −0.06 0.07 0.04 −0.01 0.00 −0.06 −0.01 −0.11 0.02 0.15* 0.04

Character

TrGrHa TrGrVi TrHe TrCoIn TrDi CaDe Br BrDe BrFl BrLLe BrLWi BrPeLe SpLLe SpLWi SpPeLe LDe LSh LSeSh LUpSuCo LLoSuCo LApSh LoFlBu FrY HaDa NuApSh NuSh NuLe NuWi NuDi NuWe SheHa SheCoIn SheRe SheTh SuOpShe MaOuShe KeLe KeWi KeTh KeWe KeSh KeCoIn KeShr KePu KeTa DoKePer BlNuPer

1 0.22** −0.15* 0.23** 0.48** 0.62** 0.60** 0.20** 0.20** 0.09 0.18* 0.05 0.07 0.07 0.47** 0.06 −0.09 0.15* 0.18* 0.01 0.02 0.33** −0.04 −0.04 −0.09 0.00 0.15* 0.07 0.05 −0.11 0.14 0.06 0.07 0.04 −0.03 −0.03 0.09 0.07 0.07 −0.11 −0.06 −0.21** −0.01 0.08 0.14 −0.08

TrGrVi

1 0.19** 0.54** 0.18* 0.27** 0.28** −0.23** 0.15* 0.01 0.04 0.16* 0.06 0.04 0.13 0.06 0.27** 0.04 0.12 0.03 −0.07 0.05 0.36** −0.11 0.09 0.10 0.13 0.13 0.11 −0.01 0.12 −0.07 0.03 0.12 −0.06 0.15* 0.10 0.18* 0.17* −0.01 0.01 −0.10 0.10 0.00 0.22** −0.14

TrHe

1 0.30** −0.03 0.09 0.05 −0.24** 0.04 0.07 0.04 −0.05 −0.15* −0.02 −0.07 0.00 0.15* −0.12 −0.09 −0.04 −0.15* −0.24** 0.27** −0.01 0.15* 0.10 0.09 −0.05 0.07 0.00 −0.04 −0.10 −0.01 0.02 0.05 0.15* 0.16* 0.04 0.05 −0.03 0.09 0.17* 0.09 −0.11 −0.17* 0.04

TrCoIn

1 0.17* 0.35** 0.34** −0.18* 0.14 −0.05 0.15* 0.15* 0.02 0.07 0.15* 0.12 0.10 −0.09 0.01 0.16* 0.10 −0.09 0.15* −0.12 0.02 0.11 0.15* 0.14 0.09 0.03 0.02 −0.12 0.02 0.05 −0.03 0.15* 0.17* 0.13 0.17* −0.11 0.06 −0.08 0.13 0.00 0.18* −0.06

TrDi

1 0.45** 0.55** −0.04 0.24** 0.13 0.17* −0.04 −0.04 0.08 0.69** −0.04 0.02 0.24** 0.18* 0.06 0.13 0.18* 0.04 −0.02 0.05 0.05 0.17* 0.08 0.06 0.04 0.00 −0.03 0.14 −0.06 0.04 0.05 0.05 0.05 0.10 −0.05 0.16* −0.08 −0.07 −0.02 0.07 −0.04

CaDe

1 0.73** 0.05 0.19** 0.03 0.23** −0.01 −0.01 0.12 0.44** 0.07 0.04 0.07 0.06 0.14 0.03 0.15* 0.17* −0.05 0.04 0.01 0.15* −0.01 0.05 −0.01 0.10 0.03 0.08 0.04 −0.10 0.05 0.16* 0.12 0.07 −0.14 0.07 −0.14 0.07 −0.06 0.07 0.00

Br

Table 4 Simple correlations among the morphological variables utilized in the studied almond genotypes.

1 0.02 0.19** 0.04 0.17* 0.00 −0.05 0.08 0.48** 0.13 −0.03 0.15* 0.11 0.10 −0.03 0.21** 0.12 −0.06 0.05 0.10 0.19** 0.06 0.05 −0.05 −0.02 0.06 0.13 0.06 0.05 0.11 0.12 0.11 0.10 −0.12 0.00 −0.17* 0.07 −0.04 0.08 −0.05

BrDe

1 0.02 0.02 0.00 0.02 0.10 0.03 0.03 0.00 −0.18* 0.01 0.08 0.13 −0.23** 0.20** −0.18** −0.07 −0.02 −0.07 −0.01 −0.03 −0.08 −0.06 −0.01 0.09 −0.03 0.04 0.10 −0.10 −0.02 −0.02 −0.04 −0.04 −0.02 −0.11 −0.11 0.10 0.05 0.00

BrFl

1 0.67** 0.60** 0.36** 0.11 0.29** 0.21** 0.06 0.32** 0.14 0.13 0.14 −0.13 0.19** 0.22** 0.17* 0.13 0.24** 0.21** 0.13 0.22** 0.02 0.00 −0.10 0.13 −0.02 0.12 0.18* 0.11 0.19** 0.23** −0.04 0.05 −0.17* −0.02 −0.02 0.07 −0.05

BrLLe

1 0.36** 0.13 0.12 0.13 0.20** −0.20** 0.19** 0.15* 0.11 −0.05 −0.13 0.13 0.08 0.12 0.12 0.16* 0.10 0.03 0.11 0.07 0.01 −0.07 −0.03 −0.05 0.09 0.16* 0.07 0.13 0.21** 0.04 0.05 −0.08 −0.07 −0.01 −0.01 −0.05

BrLWi

1 0.26** 0.00 0.47** 0.22** 0.06 0.11 0.04 −0.05 0.11 0.00 0.14 0.14 0.13 0.02 0.11 0.13 0.03 0.10 0.01 −0.03 −0.07 0.04 0.00 0.04 0.02 0.07 0.07 0.12 −0.08 0.06 −0.13 0.03 −0.08 0.01 0.06

BrPeLe

1 0.52** 0.60** −0.09 0.14 0.23** 0.09 0.02 0.08 0.11 0.11 0.13 0.06 0.07 0.17* 0.15* 0.14 0.08 −0.13 0.01 0.01 0.17* 0.10 0.09 0.06 0.05 −0.02 0.08 0.03 −0.06 −0.06 0.04 0.10 0.07 −0.04

SpLLe

1 0.36** 0.06 −0.02 0.00 0.13 −0.08 −0.02 0.16* 0.13 −0.17* −0.02 0.06 0.08 0.05 0.02 −0.02 −0.09 0.08 0.05 0.13 0.07 −0.03 −0.03 0.01 −0.13 0.01 0.04 −0.09 −0.09 −0.03 0.18* 0.05 0.05

SpLWi

5

1 −0.01 −0.12 0.23** 0.09 0.03 0.21** 0.19** −0.12 −0.01 0.05 0.07 0.13 0.02 0.03 0.02 −0.09 0.03 0.11 −0.09 0.00 0.01 0.04 −0.02 0.11 −0.10 0.06 −0.16* −0.10 −0.06 0.04 0.05

LDe

(continued on next page)

1 0.10 0.07 0.10 0.07 −0.02 0.12 0.14 0.11 0.13 0.09 0.07 0.18* 0.20** 0.12 0.13 −0.18* −0.05 0.04 0.17* 0.09 0.04 0.08 0.06 0.05 0.12 0.03 0.12 −0.06 0.10 0.07 0.07 −0.01

SpPeLe

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1 −0.01 −0.12 0.23** 0.09 0.03 0.21** 0.19** −0.12 −0.01 0.05 0.07 0.13 0.02 0.03 0.02 −0.09 0.03 0.11 −0.09 0.00 0.01 0.04 −0.02 0.11 −0.10 0.06 −0.16* −0.10 −0.06 0.04 0.05

SheCoIn

TrGrHa TrGrVi TrHe TrCoIn TrDi CaDe Br BrDe BrFl BrLLe BrLWi BrPeLe SpLLe SpLWi SpPeLe LDe LSh LSeSh LUpSuCo LLoSuCo LApSh LoFlBu FrY HaDa NuApSh NuSh NuLe NuWi NuDi NuWe SheHa SheCoIn SheRe SheTh SuOpShe MaOuShe KeLe KeWi KeTh KeWe KeSh KeCoIn KeShr KePu KeTa DoKePer BlNuPer

Character

TrGrHa TrGrVi TrHe TrCoIn

LDe

Character

Table 4 (continued)

SheRe

1 −0.10 0.05 −0.02 0.21** −0.05 0.03 0.10 0.00 −0.02 0.06 0.01 0.03 0.07 −0.11 −0.02 0.07 0.10 0.05 −0.03 −0.04 −0.03 −0.04 −0.04 −0.04 −0.02 −0.12 0.09 0.07 −0.02 −0.06

LSh

SheTh

1 0.12 0.16* −0.11 −0.10 −0.23** 0.48** 0.01 0.13 0.16* 0.14 0.12 0.15* 0.15* 0.07 −0.23** 0.08 0.03 −0.05 0.22** 0.13 0.09 0.11 −0.09 0.06 0.10 0.03 −0.08 −0.04 −0.03

LSeSh

SuOpShe

1 0.51** 0.02 −0.02 0.28** 0.10 0.06 0.09 0.09 0.13 0.15* 0.13 −0.12 −0.10 0.01 0.21** 0.11 0.03 0.03 0.05 0.00 0.12 0.03 0.05 0.07 −0.01 −0.08 −0.03 0.00

LUpSuCo

MaOuShe

1 −0.02 −0.10 0.25** 0.15* 0.02 −0.10 0.01 0.11 0.16* 0.12 −0.13 0.05 0.08 0.08 0.08 −0.03 −0.02 0.11 0.16* 0.13 −0.07 0.07 0.00 −0.03 −0.01 0.11 −0.09

LLoSuCo

KeLe

1 0.01 0.05 0.07 −0.07 0.07 −0.02 0.07 0.12 0.14 −0.04 −0.01 −0.02 0.06 −0.01 0.09 0.04 0.06 0.18* 0.16* 0.02 0.04 −0.09 0.02 −0.02 0.10 0.01

LApSh

KeWi

1 0.04 −0.39** 0.11 0.08 −0.09 −0.05 −0.10 −0.10 0.04 0.07 −0.13 0.10 −0.13 −0.01 −0.16* −0.26** −0.29** −0.20** 0.19** −0.07 −0.11 0.01 −0.03 −0.15* 0.12

LoFlBu

KeTh

1 −0.22** −0.10 −0.08 −0.04 0.05 0.05 0.02 −0.23** −0.09 0.25** 0.08 0.14 0.02 −0.10 0.01 0.06 0.04 0.03 −0.15* −0.21** −0.15* 0.07 0.03 −0.12

FrY

KeWe

1 0.02 0.17* 0.36** 0.26** 0.22** 0.30** 0.07 0.14 −0.18* 0.18** 0.17* 0.07 0.38** 0.28** 0.20** 0.22** −0.13 0.12 0.03 0.20** −0.13 0.08 0.01

HaDa

KeSh

1 0.24** 0.20** −0.09 −0.12 −0.03 0.12 0.07 −0.19** −0.02 −0.07 0.04 0.09 −0.13 −0.07 −0.03 0.22** −0.01 −0.14 0.02 −0.08 −0.11 0.03

NuApSh

KeCoIn

1 0.46** 0.09 −0.06 0.19** 0.02 −0.04 −0.16* 0.10 −0.07 0.11 0.51** 0.06 −0.07 0.19** 0.32** 0.01 0.06 0.13 −0.06 −0.08 0.05

NuSh

KeShr

1 0.58** 0.45** 0.63** −0.12 0.05 −0.11 0.40** 0.10 0.28** 0.78** 0.44** 0.10 0.49** −0.02 0.11 −0.02 0.19** −0.05 0.05 −0.01

NuLe

KePu

1 0.78** 0.74** −0.27** 0.20** −0.02 0.64** 0.11 0.20** 0.54** 0.70** 0.14 0.57** −0.32** 0.13 0.03 0.10 0.01 0.22** 0.12

NuWi

KeTa

1 0.67** −0.22** 0.04 0.01 0.58** 0.05 0.19** 0.42** 0.56** 0.29** 0.62** −0.27** 0.07 0.11 0.01 0.11 0.41** 0.07

NuDi

BlNuPer

1 −0.06 −0.34** −0.34** −0.35** −0.02 −0.01 −0.16* 0.05 −0.07 0.11 0.09 −0.09 0.05 0.01 −0.04 0.02

SheHa

(continued on next page)

DoKePer

1 −0.33** 0.15 −0.06 0.56** 0.18* 0.16* 0.60** 0.62** 0.18* 0.59** −0.22** 0.08 0.01 0.13 −0.05 0.19** −0.11

NuWe

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1 −0.08 0.22** 0.09 0.12 0.03 0.12 −0.11 −0.06 −0.12 0.13 −0.05 0.02 −0.05 0.02 −0.01

TrDi CaDe Br BrDe BrFl BrLLe BrLWi BrPeLe SpLLe SpLWi SpPeLe LDe LSh LSeSh LUpSuCo LLoSuCo LApSh LoFlBu FrY HaDa NuApSh NuSh NuLe NuWi NuDi NuWe SheHa SheCoIn SheRe SheTh SuOpShe MaOuShe KeLe KeWi KeTh KeWe KeSh KeCoIn KeShr KePu KeTa DoKePer BlNuPer

1 0.10 0.32** −0.04 −0.13 −0.02 −0.04 −0.04 −0.11 −0.14 −0.06 −0.13 0.03 0.01 0.01

SheRe

1 0.15* 0.13 0.30** 0.31** −0.12 0.17* −0.20** 0.07 0.07 0.03 0.01 0.04 0.10

SheTh

1 −0.12 0.10 0.10 −0.05 −0.02 −0.08 −0.15* −0.02 0.09 −0.01 −0.07 −0.06

SuOpShe

1 0.28** 0.11 0.15* 0.21** −0.06 0.06 0.00 0.02 −0.13 −0.07 0.02

MaOuShe

For explanation of the character symbols, see Table 1. * , **. Correlation is significant at the 0.05 and 0.01 levels, respectively.

SheCoIn

Character

Table 4 (continued)

1 0.59** 0.22** 0.64** 0.06 0.05 0.01 0.19** 0.08 0.06 −0.05

KeLe

1 0.25** 0.63** −0.38** 0.11 −0.04 0.08 0.10 0.20** −0.03

KeWi

1 0.55** −0.03 0.02 −0.08 −0.05 0.06 0.43** −0.17*

KeTh

1 −0.10 −0.03 −0.16* 0.03 −0.02 0.42** −0.02

KeWe

1 −0.13 −0.03 −0.02 0.05 −0.04 −0.05

KeSh

1 0.35** 0.10 −0.13 0.00 −0.01

KeCoIn

1 0.05 0.02 −0.14 −0.04

KeShr

1 −0.13 −0.06 0.00

KePu

1 0.14 −0.10

KeTa

1 −0.04

DoKePer

1

BlNuPer

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genotypes studied were highly fertile. The values of the most important fruit traits for the selected superior genotypes are presented in Table 3.

which corresponds with previous results (Talhouk et al., 2000; Sorkheh et al., 2009). Fruit yield was positively correlated with tree growth habit (r = 0.19), tree growth vigor (r = 0.33), branch leaf length (r = 0.19), and leaf density (r = 0.19), and agreed with the previous findings (Khadivi-Khub and Etemadi-Khah, 2015; Sepahvand et al., 2015; Khadivi-Khub and Osati, 2015). Harvest date was positively correlated with tree height (r = 0.36) and leaf serration shape (r = 0.48), while it showed negative correlations with the location of flower bud (r = -0.39) and fruit yield (r = -0.22), which is in accordance with previous results (Talhouk et al., 2000; Sorkheh et al., 2010; Zeinalabedini et al., 2012; Khadivi-Khub and Etemadi-Khah, 2015). Nut weight showed positive correlations with branch leaf length (r = 0.22), harvest date (r = 0.30), nut shape (r = 0.19), nut length (r = 0.63), nut width (r = 0.74), and nut diameter (r = 0.67), which corresponds with previous results (Khadivi-Khub and Etemadi-Khah, 2015; Sepahvand et al., 2015; Khadivi-Khub and Osati, 2015). Correlation results show that nut thickness could be a powerful indicator for selecting high-performing

3.2. Correlations among characters The correlations showed highly significant values, especially for the fruit characters (Table 4). Tree growth vigor showed positive correlations with tree height (r = 0.22), trunk diameter (r = 0.23), canopy density (r = 0.48), branching (r = 0.62), branch density (r = 0.60), and branch flexibility (r = 0.20), in agreement with other findings (Talhouk et al., 2000; Sorkheh et al., 2009; Khadivi-Khub and Etemadi-Khah, 2015). Canopy density showed positive correlations with branching (r = 0.45), branch density (r = 0.55), and leaf density (r = 0.69), which corresponds with previous results (Zeinalabedini et al., 2012; Khadivi-Khub and Etemadi-Khah, 2015). Branch leaf length was positively correlated with branch leaf width (r = 0.67) and branch petiole length (r = 0.60) and also spur leaf length showed positive correlations with spur leaf width (r = 0.52) and spur petiole length (r = 0.62),

Table 5 Eigenvalues of the principal component axes from PCA of morphological characters in the studied almond genotypes. Component Character Tree growth habit Tree growth vigor Tree height Trunk color intensity Trunk diameter Canopy density Branching Branch density Branch flexibility Branch leaf length Branch leaf width Branch petiole length Spur leaf length Spur leaf width Spur petiole length Leaf density Leaf shape Leaf serration shape Leaf upper surface color Leaf lower surface color Leaf apex shape Location of flower bud Fruit yield Harvest date Nut apex shape Nut shape Nut length Nut width Nut diameter Nut weight Shell hardness Shell color intensity Shell retention Shell thickness Suture opening of the shell Marking of outer shell Kernel length Kernel width Kernel thickness Kernel weight Kernel shape Kernel color intensity Kernel shriveling Kernel pubescence Kernel taste Double kernel percentage Blank nut percentage Total % of Variance Cumulative %

1 −0.02 0.02 0.03 0.07 0.08 0.07 0.02 0.08 −0.08 0.15 0.08 0.03 0.07 0.01 0.11 0.05 0.04 0.15 0.10 0.06 0.02 −0.11 −0.05 0.30 −0.01 0.21 0.73** 0.88** 0.80** 0.85** −0.24 0.12 −0.04 0.64** 0.10 0.24 0.75** 0.77** 0.18 0.69** −0.30 0.07 0.03 0.12 0.12 0.22 0.04 5.33 11.34 11.34

2 −0.12 0.78** 0.28 −0.02 0.36 0.74** 0.81** 0.82** 0.14 0.17 0.07 0.19 −0.09 0.03 0.05 0.75** 0.03 −0.14 0.16 0.10 0.08 0.12 0.28 −0.05 −0.10 0.05 0.01 0.14 −0.02 −0.02 0.02 0.03 0.04 0.08 −0.03 −0.05 0.02 0.09 0.01 0.04 −0.12 0.09 −0.20 0.02 0.02 0.06 −0.01 3.66 7.79 19.12

3 −0.37 −0.10 0.67** 0.62** 0.58** 0.01 0.20 0.16 −0.48 0.13 0.03 0.01 0.14 −0.08 −0.04 −0.13 0.03 0.56** −0.06 0.03 0.00 −0.12 −0.30 0.55** −0.17 0.11 0.06 0.03 0.01 0.05 0.06 0.06 −0.10 −0.03 0.16 −0.05 0.17 0.08 0.14 0.07 −0.04 −0.02 0.11 0.07 −0.13 −0.03 −0.03 2.59 5.51 24.63

4 −0.09 0.05 −0.07 0.08 −0.06 0.13 0.07 0.02 −0.04 0.82** 0.70** 0.79** 0.26 −0.04 0.42 0.16 −0.03 0.24 0.04 0.01 0.06 −0.11 0.13 0.18 0.33 0.03 0.13 0.06 −0.03 0.11 0.02 −0.02 −0.07 −0.02 −0.01 0.04 0.02 0.00 0.14 0.13 −0.02 0.10 −0.16 −0.10 −0.16 −0.04 −0.03 2.48 5.27 29.90

5 −0.01 0.09 0.14 −0.18 0.14 −0.07 0.00 −0.02 0.18 0.16 0.05 0.12 0.81** 0.82** 0.63** −0.04 0.02 0.14 0.09 −0.06 0.02 0.22 0.13 −0.07 −0.11 0.06 0.07 0.09 0.08 −0.06 −0.08 0.02 0.01 0.14 0.06 0.04 −0.01 −0.02 −0.12 −0.02 0.06 −0.04 −0.03 0.08 0.30 0.08 0.03 2.17 4.61 34.51

6 0.23 0.07 0.07 0.06 −0.03 −0.08 0.02 0.06 0.04 −0.07 −0.07 0.03 0.06 0.05 0.13 −0.03 0.04 −0.29 0.08 0.06 0.03 −0.11 0.43 −0.11 −0.22 −0.08 −0.02 0.08 0.02 0.15 −0.74** −0.03 0.66** 0.20 0.65** −0.09 −0.10 0.03 −0.09 −0.06 −0.05 −0.20 0.04 −0.07 −0.14 −0.07 −0.08 2.06 4.39 38.90

7 0.37 0.08 0.33 −0.18 0.23 0.02 0.01 −0.02 0.01 0.03 −0.02 0.05 0.02 −0.04 0.08 0.00 −0.16 −0.13 −0.07 0.12 0.29 −0.15 0.13 0.02 −0.15 −0.13 −0.09 0.05 0.28 0.07 0.01 −0.08 −0.06 −0.22 −0.11 −0.06 −0.01 0.14 0.67** 0.47 0.09 0.03 −0.15 −0.07 −0.01 0.76** −0.09 2.04 4.35 43.25

8

8 0.22 −0.08 0.11 0.07 −0.06 0.04 −0.07 −0.01 −0.02 0.06 0.09 −0.07 0.02 0.05 0.02 0.04 −0.05 −0.04 0.11 −0.11 0.10 0.10 0.01 0.07 0.40 0.81** 0.39 −0.13 −0.20 0.04 0.01 −0.10 −0.20 −0.04 0.00 0.04 0.43 −0.16 −0.06 0.07 0.69** −0.08 0.03 0.05 0.00 −0.09 −0.03 1.94 4.12 47.37

9 0.09 0.08 0.09 −0.24 −0.19 0.21 −0.06 0.04 −0.01 0.12 0.10 −0.12 0.08 0.00 −0.05 0.09 0.04 0.31 0.82** 0.79** −0.06 −0.06 0.29 0.20 0.07 −0.04 0.00 0.03 0.16 0.07 −0.05 −0.07 0.00 0.15 0.08 0.00 −0.07 −0.07 0.07 0.04 0.03 0.03 0.06 −0.04 −0.14 0.00 −0.06 1.86 3.95 51.32

10 0.24 0.10 −0.03 0.05 −0.17 −0.17 0.10 0.08 0.58** 0.10 0.11 −0.05 −0.03 −0.03 −0.11 −0.21 0.02 0.14 −0.02 0.07 0.05 −0.79** −0.01 0.36 −0.18 0.07 0.05 −0.04 −0.07 −0.06 0.08 −0.02 0.07 −0.18 0.16 0.04 0.16 0.22 0.18 0.06 −0.18 0.01 0.05 0.01 0.18 0.01 −0.02 1.64 3.49 54.81

11 0.05 −0.14 −0.07 0.19 −0.01 0.14 −0.02 −0.08 −0.02 −0.07 −0.03 0.03 −0.05 −0.09 0.16 0.02 −0.13 0.00 0.07 0.01 0.08 −0.08 −0.19 0.04 −0.18 0.04 −0.02 0.08 0.08 0.05 −0.11 0.01 −0.12 0.12 −0.15 0.00 −0.06 0.00 −0.06 −0.17 −0.06 0.76** 0.79** 0.07 −0.06 −0.05 −0.07 1.57 3.33 58.14

12 −0.08 0.00 0.00 −0.02 0.17 −0.05 0.09 0.12 0.10 0.06 −0.32 0.14 0.15 −0.15 0.14 −0.10 0.79** −0.14 0.02 −0.02 0.64** 0.00 0.00 0.14 0.05 −0.01 −0.02 0.01 0.09 0.09 −0.11 −0.04 −0.02 0.18 −0.03 0.05 −0.09 −0.10 0.02 −0.07 0.02 0.01 −0.09 0.03 0.09 0.03 −0.02 1.46 3.10 61.24

13 0.34 0.18 0.21 −0.18 −0.01 −0.03 0.05 −0.06 0.07 0.04 −0.05 −0.04 0.04 0.04 −0.10 −0.13 −0.05 0.09 −0.13 0.05 0.00 0.08 −0.04 0.17 0.18 −0.05 0.02 0.11 −0.01 0.12 −0.09 0.85** −0.20 0.24 0.12 0.07 −0.10 −0.02 −0.20 −0.22 −0.10 0.12 −0.10 −0.04 −0.14 0.04 −0.07 1.40 2.99 64.22

14 −0.09 −0.01 0.02 −0.03 0.07 −0.12 0.13 0.09 −0.09 −0.12 −0.20 0.12 0.05 −0.09 0.25 −0.12 0.07 0.00 0.01 −0.01 −0.08 −0.02 −0.15 0.27 0.19 0.05 0.20 −0.01 −0.13 0.07 0.08 −0.01 −0.09 −0.13 0.20 −0.02 0.12 0.05 −0.01 0.04 −0.07 0.18 −0.08 0.79** −0.44 −0.07 −0.03 1.37 2.91 67.13

15 0.23 −0.12 −0.10 0.05 −0.08 0.01 0.03 −0.05 0.06 −0.06 −0.11 0.11 −0.03 0.04 0.03 0.14 −0.14 0.03 0.08 −0.12 0.14 0.09 −0.16 0.11 −0.03 0.10 −0.04 0.13 0.07 −0.09 0.00 −0.07 −0.01 0.17 −0.05 −0.04 −0.13 −0.02 −0.21 −0.03 −0.12 −0.04 −0.04 −0.06 −0.35 −0.01 0.86** 1.27 2.70 69.83

16 −0.08 −0.06 −0.06 0.13 0.04 0.01 −0.05 0.05 0.17 0.06 0.12 −0.05 0.03 0.02 −0.05 0.01 −0.11 −0.14 0.02 0.00 0.25 0.05 0.13 −0.10 −0.11 0.08 0.11 0.04 0.00 0.03 0.02 0.09 0.04 −0.05 −0.18 0.83** 0.12 0.00 0.18 0.18 −0.04 0.08 −0.07 −0.02 −0.40 −0.20 −0.02 1.26 2.68 72.51

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almond genotypes in the field (Sorkheh et al., 2009). In addition, shell hardness was negatively correlated with fruit yield (r = - 0.23), nut width (r = - 0.27), nut diameter (r = - 0.22), and nut weight (r = - 0.33) and agreed with the previous results (Sanchez-Perez et al., 2007; Zeinalabedini et al., 2012; Khadivi-Khub and EtemadiKhah, 2015). This result indicates that a softer shell is accompanied by a higher kernel-to-shell ratio and that soft-shell cultivars have a tendency to bear relatively larger kernels (i.e. more kernel than the shell). In addition, shell thickness was positively correlated with nut length (r = 0.40), nut width (r = 0.64), nut diameter (r = 0.58), and nut weight (r = 0.56), while it was negatively correlated with shell hardness (r = - 0.34). Kernel weight showed positive correlations with branch leaf width (r = 0.23), branch leaf length (r = 0.21), harvest date (r = 0.22), nut shape (r = 0.19), nut length (r = 0.49), nut width (r = 0.57), nut diameter (r = 0.62), nut weight (r = 0.59), kernel length (r = 0.64), kernel width (r = 0.63), and kernel thickness (r = 0.55) and agreed with the previous results (Sanchez-Perez et al., 2007; Zeinalabedini et al., 2012; Khadivi-Khub and Etemadi-Khah, 2015; Gouta et al., 2019). Double kernel percentage showed a negative correlation with location of flower bud (r = - 0.15). No correlation was observed between kernel weight and shell hardness, so these traits were considered to be independent. These results are in accordance with the previous reports (Sanchez-Perez et al., 2007; Sorkheh et al., 2010; Khadivi-Khub and Etemadi-Khah, 2015; Gouta et al., 2019), that noted that shell softness does not affect kernel weight. High absolute correlation values between morphological and pomological traits related to fruit, nut, leaf size, and phenology have also been established for other species of the genus Prunus, such as plum (Khadivi-Khub and Barazandeh, 2015), apricot (Badenes et al., 1998; Khadivi-Khub and Khalili, 2017), peach (Nikolic et al., 2010), and sour cherry (Khadivi-Khub et al., 2013). On this basis, it can be concluded that these characters have a similar effect on determining cultivar cropping potential and also germplasm characterization. Furthermore, these data can be exploited either by breeding programs or for facilitating the identification of almond ecotypes during field surveys.

Fig. 1. Bi-plot of PC1/PC2 plane showing the relationships between the studied almond genotypes. The symbols represent the genotypes in the plot including Anaj (A), Anjedan (An), Evand (E), Ghanat (G), Javersian (J), Karchan (Ka), Khalaj (Kh), Kolbodagh (K), Molabagher (M), Nodeh (N), Saghi (S), Savarabad (So), and Zolfaghar (Z).

nut diameter, nut weight, shell thickness, kernel length, kernel width, and kernel weight. Furthermore, starting from negative to positive values of PC2, the genotypes indicated gradual increases in tree growth vigor, canopy density, branching, branch density, and leaf density. In addition, a tri-plot was prepared according to the PC1, PC2, and PC3 that reflected relationship among the genotypes in terms of phenotypic resemblance. Results of tri-plot supported the bi-plot and the genotypes were distributed in the plot (Fig. 2). The large phenotypic diversity was observed among the studied genotypes that it was expected since almond is self-incompatible and traditional farmers tend to propagate almond by seed. Although it is a negative trait, the self-incompatibility shown by almond has the advantage of maintaining genetic variability within its populations (Gradziel and Martinez-Gomez, 2013; Khadivi-Khub and Etemadi-Khah, 2015). The large variability observed in the measured characters is an indicator of a high level of genetic diversity among the almond genotypes studied.

3.3. Principal component analysis (PCA) The PCA was performed to identify the main distinguishing characteristics of the variability. As a criterion for extracting the main components, eigenvalues greater than 1.00 were taken to determine which of the PC scores represented the greatest value of variation. For each factor, the load values above 0.55 were considered significant, which indicated 16 components that explained 72.51% of the total variance (Table 5). The first three components explained 24.63% of the observed total variance that 11.34% of the variance was accounted for PC1, followed by 7.79% for PC2 and 5.51% for PC3. Eight characters including nut length, nut width, nut diameter, nut weight, shell thickness, kernel length, kernel width, and kernel weight were found to be influential for PC1 and thus called as fruit factor. Similarly, Gouta et al. (2019) reported that nut length, nut thickness, and nut size make the biggest contribution to the positive PC1. In addition, it has been reported that nut traits were consistent in their contribution to the PC1 and could be used as a tool for almond germplasm characterization (Talhouk et al., 2000; Sorkheh et al., 2009; Khadivi-Khub and Etemadi-Khah, 2015). The characters including tree growth vigor, canopy density, branching, branch density, and leaf density showed positive and significant correlations with PC2 and thus called as vegetative traits factor. The PC3 was correlated with tree height, trunk color intensity, trunk diameter, leaf serration shape, and harvest date. The remaining characters loaded significantly in the rest components (PC4-PC16) and explained less variability. The projection of the studied genotypes on the PC1/PC2 plot is presented in Fig. 1. By starting from negative toward positive values of PC1, the genotypes showed gradual increases in nut length, nut width,

Fig. 2. Tri-D plot for the studied almond genotypes based on the PC1/PC2/PC3. The symbols represent the genotypes in the plot Anaj (A), Anjedan (An), Evand (E), Ghanat (G), Javersian (J), Karchan (Ka), Khalaj (Kh), Kolbodagh (K), Molabagher (M), Nodeh (N), Saghi (S), Savarabad (So), and Zolfaghar (Z). 9

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Similarly, large distributions have been observed in native germplasm characterized using morphological traits in Morocco (Lansari et al., 1994), Lebanon (Talhouk et al., 2000; Chalak et al., 2007), Italy (De Giorgio et al., 2007), Turkey (Ak et al., 2005), Iran (Fathi et al., 2008; Sorkheh et al., 2010; Khadivi-Khub and Etemadi-Khah, 2015; Sepahvand et al., 2015; Khadivi-Khub and Osati, 2015), Serbia (Colic et al., 2012), and Tunisia (Gouta et al., 2019). Because precipitation has been low in recent years, scarce water supplies necessitate careful management of agricultural crop irrigation in many regions of the world (Khadivi-Khub et al., 2016). Thus, cultivation of fruit crops with having resistance to drought condition and suitable performance helps to decrease irrigation practices. Egea et al. (2010) described the almond as one of the fruit tree species that best responds to reduced water in deficit irrigation programs, maintaining its commercial value with a suitable kernel size.

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4. Conclusions The success of any breeding program is highly dependent on the extent of genetic diversity and also knowledge of the behavior of desirable traits through crosses. In the present research, the morphological and pomological traits were used to determine phenotypic diversity among almond genotypes. The knowledge of tree characters, leaf properties and fruit attributes of the genotypes studied here could be useful to choose the appropriate ones to be grown under different climatic conditions or used as a parent in future breeding programs. The studied genotypes showed high phenotypic variability and consequently could be considered as a potential resource of germplasm to be exploited in almond improvement. Regarding ideal values of the important and commercial characters of almond such as fruit yield, nut weight, shell hardness, kernel shape, kernel weight, and kernel taste, 24 genotypes including Khalaj-4, Ghanat-14, Ghanat-12, Karchan-2, Ghanat-15, Ghanat-1, Zolfaghar-1, Ghanat-10, Evand-44, Anaj-6, Karchan-1, Ghanat-4, Ghanat-6, Molabagher-1, Javersian-5, Ghanat-16, Zolfaghar-3, Zolfaghar-2, Javersian-12, Molabagher-16, Karchan-7, Nodeh-7, Karchan-5, and Ghanat-11 were superior and could be used as a parent in breeding programs and also might be singled out directly for cultivation in orchards. References Ak, B.E., Kuzdere, H., Kaska, N., 2005. An investigation on phenological and pomological traits of some almond cultivars grown at Ceylanpinar State farm in Turkey. Options Méditerr. 63, 43–48. Artega, N., Socias i Company, R., 2001. Heritability of fruit and kernel traits in almond. Acta Hortic. 591, 269–274. Badenes, M.L., Martínez-Calvo, J., Lacer, G., 1998. Analysis of apricot germplasm from the European ecogeographical group. Euphytica 102, 93–99. Chalak, L., Chehade, A., Kadri, A., 2007. Morphological characterization of cultivated almonds in Lebanon. Fruits 62, 177–186. Colic, S., Rakojac, V., Zec, G., Nikolic, D., Aksic, M.F., 2012. Morphological and biochemical evaluation of selected almond [Prunus dulcis (Mill.) D.A.Webb] genotypes in northern Serbia. Turk. J. Agric. For. 36, 429–438. De Giorgio, D., Leo, G., Zacheo, G., Lamascese, N., 2007. Evaluation of 52 almond cultivars from the Apulia region in Southern Italy. J. Hortic. Sci. Biotechnol. 82, 541–546. Egea, G., Nortes, P.A., González-Real, M.M., Baille, A., Domingo, A., 2010. Agronomic response and water productivity of almond trees under contrasted deficit irrigation regimes. Agric. Water Manag. 97, 171–181. Egea, J., Burgos, L., 1995. ). Double kernelled fruits in almond (Prunus dulcis Mill.) as related to pre-blossom temperature. Ann. Appl. Biol. 126, 163–168. Fathi, A., Ghareyazi, B., Haghnazari, A., Ghaffari, M.R., Pirseyedi, S.M., Kadkhodaei, S., Naghavi, M.R., Mardi, M., 2008. Assessment of the genetic diversity of almond

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